While reward is known to be a powerful and lasting force on spatial attention, its effects on sustained visual attention are not well understood. Specifically, it is unclear how reward affects dissociable aspects of sustained attention, including accuracy, response consistency (i.e., reaction time variability), and the decrement in these measures over time. The current study further examines reward and sustained attention by 1) using the gradual onset continuous performance task (gradCPT), which is sensitive to these multiple aspects of sustained attention (Esterman et al. 2012); and 2) manipulating reward with instructions that better performance would result in earlier completion of the task. In the 10-minute task, participants view scenes that gradually transition from one to the next, and are instructed to respond to city scenes (90%) and withhold for mountain scenes (10%). After completing several baseline gradCPTs with no reward, participants performed a final gradCPT with either standard instructions or instructions that the task could be completed sooner based on better performance. Though performance on the baseline gradCPTs did not differ between groups, the participants in the reward condition demonstrated improved response inhibition to mountain scenes and showed decreased reaction time (RT) variability to city scenes. Despite these reward-related performance improvements, both groups displayed parallel decrements in performance over time. This demonstrates that reward can improve response control and decrease high-frequency attentional fluctuations, suggesting that failures of these processes may be due to lack of effort or motivation. On the other hand, the decrease in performance over time failed to be modulated by reward, suggesting that the rate of depletion of cognitive resources is less malleable by motivational factors. These data indicate that dissociable mechanisms contribute to fluctuations in sustained visual attention.